Method of finishing gears



Patented July 5, 1938 UNITED STATES P T NT QFFICEI METHOD or FINISHING GEARS Oliver G. Simmons, Lakewood, Ohio,v Application April 27, 1935, Serial No. 18,676

4 Claims. (01. 90- -2) This invention relates to a method and means for finishing gears by subjecting the gears to a combined and simultaneous burnishing and shaving operation. v 5 An object of the invention is to provide an improved and novel method and means for finishing gears with a high degree of accuracy and with the desired surface smoothness, compactness and finish.

Another object is to provide an improved and novel method and means for finishing gears quickly and economically and with a high degree of accuracy and the desired surface smoothness, compactness and finish.

Another object is to provide an improved and novel method and means for finishing gearsquickly and economically and with a high degree of accuracy and the desired surface smoothness, compactness and finish by means of a combined and simultaneous burnishing and shaving operation. 1

Another object is to provide an improved and novel method and means for finishing both external and internal gears quickly and economically and with a high degree of accuracy and the desired surface smoothness, compactness and finish by means of a combined and simultaneous burnishing and shaving operation.

A further object is to provide an improved and novel method and means for finishing gears by a combined burnishing and shaving action,

which quickly, economically and by means of a single operation refines the gear teeth to a high degree of accuracy, while simultaneously burnishing the-working face surfaces of the teeth.

Another object is to provide a method for si-- same quickly, economically and with a high degree of accuracy and the desired surface smoothness, compactness and finish. Further and additional objects and advantages residing in the invention will become apparent during the detailed description that is to follow I of embodiments thereof.

Referring to the accompanying drawing, Fig. 1 is an end elevational view of a plurality of helical cutters embodying the invention arranged in intermeshing relation with a helical work gear, one of the cutters being mounted upon the spindle of a conventional milling machine or other machine tool, while. the other cutters and the work gear are mounted upon shafts arranged in an attachment, such as is shown in my co-. pending application, Serial Number 9,824, filed March '7, 1935, and which is secured to the table of the machine.

Fig. 2 is a side elevational view of one of the cutters shown in Fig. 1.

Fig. 3 is a detached and somewhat schematic side elevational view of the three cutters shown in Fig. 1, said view being on a reduced scale .and illustrating the cutters arranged one above theother to show the manner in which the circular grooves formed therein from end to end of the cutters are staggered so that the three cutters combined have a multiplicity of cutting edges which, when the cutters are rotated in mesh with a work gear, will take a multiplicity of bites or cuts in the gear extending from end to end of the gear and lying very closely adjacent to each other or actually overlapping each other.

Fig. 4 is a fragmentary developed sectional view through one of the teeth of the work gear illustrating diagrammatically the action of the cutting edges of the cuttersupon the working face surface of the tooth of the gear, and

Fig. 5 is a view similar to Fig. 3, but illustrating iznuodified forms of cutters from those shown in The present requirement for gears of highaccuracy and finish, especially gears which are to be used in motor vehicles, has necessitated further finishing operations uponthe gears after they have been cut.

L This further finishing of the gears has been carried out heretofore by means of a number of separate operations,-namely, by a shaving operation to remove and correct irregularities and errors in the gear teeth occasioned by inaccurate cutting of ,the gears, and by aseparate burnishing operation to compact, smooth and polish the, working face surfaces of the gear teeth.

.It will be evident that the practice involving separate shaving and polishing operations is necessarily slow and uneconomical.

.Machlnes have been produced and are now being used for the purpose of subjecting the gears to the shaving operation referred to. However, generally these machines impart to r the work gears and to the tools or cutters compounded relative movements, usually consisting of relatively rotating the work gears and cutters in meshand at the same time imparting to the cutters and work gears relative long, lateral and linear movements to produce the shaving action of the cutters upon the work gears. These special machines,

because of the compounded movements which they .must impart to the cutters and work gears, are relatively complicated and expensive, in view of the single purpose for which they are used, and, in addition, they are relatively slow in operation.

Certain of the machines referred ,to are constructed so that the axes of the cutter and work gear are arranged in non-parallelrelationship, wherefore the cutter has merely a tangential point contact with the work gear. It is necessary in such machines to impart long relative linear and lateral movements to the cutter and. gear axially of the latter, to cause the tangential point contact of the cutter with the gear to move across the working face surfaces of the gear teeth from end to end thereof-in order to cut cylindrical surfaces thereon.

Such machines are not adapted to operate upon internal gears because of the necessary lateral and linear movements of the cutter completely across the face of the gears, since the attaching flanges of the internal gears and the supports to which the flanges-must .be connected, restrict the operating space within the internal gears and interfere with the compounded relative rotative and long lateral and linear movements between the cutters and the work gears. The same condition exists in connection with gears formed on spline shafts, because the flanges or shoulders on the shafts adjacent to the gears interfere and prohibit the imparting to the cutters and 'work gears the compounded relative movements referred to. Likewise, the shaving of the gears of cluster gears cannot be carried out on these machines for the same reasons.

As previously stated heretofore the shaving operation must be followed bya separate burnishing operation, which not only increases the time and cost of finishing the gears, but requires separate burnishing apparatus therefor.

It is desired by means of the present invention to provide a method and means which may be used for finishing gears of different types, as for example, spur or helical external and internal gears, cluster gears, gears on spline shafts, herringbone gears and other types of gears to a high degree of accuracy, smoothness, compactness and finish, quickly and economically, by means of a single operation, and wherein the use of special complicated machines is eliminated since during the operation it is not necessary to impart to the cutters and work'gears, in addition to the movement of rotation and a radial pressure feed movement, long lateral or linear relative movements therebetween, to cause the cutting edges of the former to cut or bite into the workingface surfaces of the teeth of the work gears from end to end of the gears. In attaining the ends sought,

5 the present invention contemplates the provision allow the same some axial play to shave and burnish simultaneously the complete working face surfaces of the teeth of the work gears from end to end thereof and with a high degree of accuracy, smoothness, compactness and finish, irrespective of the degree of error of spacing or-of tooth form in the work gears after they have been cut.

In my copending application Serial No. 9,824, filed March 7, 1935, the invention disclosed th rein contemplated burnishing and shaving cutters in the form of straight tooth, helical tooth or other types of gears corresponding to the types of work gears with which they are used, and provided around their circumferences with a multiplicity of helical grooves extending from end to end of the cutters in an axial direction and completely through the teeth thereof from the outside diameters of the cutters to the roots of the teeth, whereby the teeth of the cutters are pro: vided with a multiplicity of cutting edges which act, when'the cutters are rotated under pressure in mesh with the work gears, toshave the complete working face surfaces of the teeth of the work gears from end to end of the gears, due to the lead of the circumferential helical grooves, while the working face surfaces of the teeth of the cutters between the helical grooves act to simultaneously burnish the working face surfaces of the teeth of the work gears.

The invention disclosed in the present application differs from that disclosed in my aforementioned copending application Serial No. 9,824, in

that the cutters are provided with a multiplicity of circumferential circular grooves arranged in spaced relation from end to end of the cutters as distinguished from the helical grooves referred to.

' In order that the cuts or shaving bites of the cutting edges provided in the cutters by the circular circumferential grooves will act upon the complete working face surfaces of the teeth of the gears and will migrate from end to end of the work gears, the spaced circular circumferential grooves in each cutter are staggered or offset with relation to the spaced circular circumferential grooves in the other cutters of the group of cutters acting upon the work gears. Therefore, since the cutters are each provided with a plurality or multiplicity of such spaced circumferential circular grooves andthe grooves in each cutter are staggered or offset with respect to the grooves of the other cutters, the shaving bites or cuts taken in the work gears by the large number of cutting edges formed by the grooves will lie in closely juxtaposed relationship or will overlap and will extend from end to end of the working face surfaces of the teeth of the work gears.

In view of the fact that the cutters are each provided with a plurality of spaced circumferential circular grooves staggered or offset with respect to the grooves in the other cutters and extending completely through the teeth of the cutters from the outside diameter thereof to the roots of the teeth, it is necessary, to eifect the simultaneous shaving and burnishing of the entire 'working face surfaces of the teeth of the work gears from end to end of the gears, to impart only a relative rotative movement to the the cutters, act upon the working face surfaces of the teeth of the work gear in such close proximity to each other that any axial movement or axial play which the cutters have will be so slight as not to interfere with the practice of the invention upon internal gears, spline shaft gears, cluster gears, or the like, particularly since the axes of the cutters and work gears are arranged in parallel relationship. 1

As previously stated, the invention may be practiced upon the usual burnishing machine, wherein the work gear and the burnishing gears are simply rotated in mesh under pressure, or it may be practiced by means of simple attachments which canbe mounted upon the ordinary milling machine, lathe, or other machine tool, inasmuch as any relative movement imparted to the cutters and work gear in addition to the rotative and pressure feed movements would consist simply in a very slight axial movement or axial play.

In describing the invention in detail, reference will first be made to Figs. 1 to 4 inclusive of the drawing, wherein an external helicalwork gear is shown being simultaneously shaved and bur-' nished by means of a plurality of helical cutters.

The helical work gear, indicated at 6, may be of either hand, any desired angle of helix, normal diametral pitch, normal pressure angle, and number of teeth. a

The tools or cutters, indicated at I, 8 and 9 respectively, are in the form of helical gears of, the opposite hand from the work gear 6, but are of the same angle of helix, normal diametral pitch v and normal pressure angle as the work gear.

Although the cutters may be of the same size and number of teeth as the work gear, it is preferable in the case of external gears to employ cutters which are of larger size and greater number of teeth than the work gear, because of the better results thus obtained, due to the greater number of cutting edges, the increased burnishing and peripheral surfaces, and the longer wearing qual ities of the cutters. Consequently the work gear 6 has been illustrated herein as of smaller size and lesser number of teeth than the cutter 1, 8 and 9, it being noted that the cutters themselves are shown, by way of example, as all of the same size and number of teeth.

As previously stated, the cutters employed in practicing the invention are provided with a plurality or multiplicity of spaced circumferential circular grooves extendingfrom end to end of the cutters in an axial direction and completely through the teeth thereof from the outside diameters of the cutters to the roots of the teeth.

The cutters I, 8 and 9 may be provided with the same number of spaced circumferential circular grooves or the various cutters may be provided with different numbers of the grooves. The cutters I, 8 and 9 have been illustrated herein, by way of example, as each provided with four axially spaced circumferential circular grooves ID.

The circular grooves Ill preferably are spaced from end to end of the cutters in an axial direction and should be of sufficient number to form a great multiplicity of cutting edges II and I! on both of the working face surfaces of each of the teeth of the cutters. The great number of cutting edges H and I2 formed on the teeth of the cutters 1, 8 and 9 by the spaced circumferential circular grooves I0 act, when the cutters are rotated in mesh with-the work gears under pressure, to

The large number or multiplicity of cutting or shaving edges II and [2 on the cutters reduces the cutting or shaving force which must be applied to the cutters in shaving the work gears and enables the cutters to be used upon conventional burnishing machines or upon attachments mounted on conventional machine tools.

Reference to Fig. 3 of the drawing will show that the circumferential grooves II] are spaced axially of the cutters I, 8 and 9 with the grooves and the cutting edges H and I 2 formed thereby so arranged in the various cutters as to lie in staggered or offset relationship with respect to the grooves and cutting edges in the other cutters, wherefore the shaving bites or cuts taken by the cutting edges II and I2 in the working face surfaces of the work gears will lie very closely adjacent to each other and will extend from end to end of the work gears. This arrangement enables the work gears to be shaved and burnished by the cutters by simply rotating the cutters and work gears in mesh under pressure, although it is preferable in order to obtain better results and smooth accurate working face surfaces on the teeth of the work gears to allow a slight axial play to the cutters or to impart avery smallaxial movement thereto, to cause the shaving cuts or bites to overlap.

As previously stated, the grooves l0 extend completely through the teeth T of the cutters l, 8 and 9 from the outside diameters D thereof to the roots R of the teeth. The teeth T of the cutters are divided by the circular grooves II) from end to end of the cutters into a plurality of, separate small cutting and burnishing teeth, each of which in the case of helical cutters, has two obtuse cutting or shaving edges l2 and two acute shaving or cutting edges II. The working face surfaces of the teeth T between the grooves I0 form a plurality of burnishing surfaces which, when the cutters are rotated in mesh with the work gear under pressure, act to burnish uniformly the working face surfaces of the teeth of the work gear from end to end of the gear simultaneously as they are being shaved.

It will be understood that the cutters I, B and 9 may be employed upon the usual burnishing machine and run in mesh with the work gear under pressure to shave and burnish the working face surfaces of the teeth of the work gear. In addition to practising the invention upon the usual burnishing machine, it might be practised by means of an attachment which could be secured to the table or slide of a machine tool, such as a milling machine, and corresponding to theattachment shown in my said copending application Serial No. 9,824. The attachment shown in my said copending application carries two of the cutters and the work gear while the third cutter is mounted on the spindle of the machine. Of course, the invention can be practised upon any apparatus capable of supporting a plurality of cutters in mesh with the work gear on axes parallel to the axis thereof and rotating the same while applying a radial pressure feed therebetween.

It will be understood that the rotation of the cutters in mesh with the work gear causes the large number of cutting edges H and 12 formed by the plurality of staggered or offset circumferential circular grooves III to take small cuts or shaving bites in the working face surfaces of the teeth of the work gear, which cuts or shaving bites, due to the great number of staggered or offset cutting or shaving edges, lie so closely adail.

jacent one another as to substantially overlap or merge together and to extend from end to end of the work gear in an axial direction. It will be seen that should there be any intervals between the shaving cuts or bites a slight axial play or movement of the cutters during the operation would eliminate such intervals and would result in a complete overlapping of the shaving cuts or bites.

Inasmuch as the shaving bites or cuts taken by the cutting edges H and i2 are each exceedingly small, the chips being like powder or the filings from a fine file, wherefore only relatively small pressures are required, the cutters and work gear may be rotatedat high speeds, since relatively small torque is required'to cause the cutters to perform their cutting or shaving action upon the teeth of the work gear. Also, during the rotation of the cutters in mesh with the work gear under pressure, the working face surfaces of the teeth T between the grooves Hi rolling in mesh with the working face surfaces of the teeth of the work gear, act to burnish the latter and to provide the desired smoothness, compact-- ness and finish thereon. It has been found that, due to the, combined shaving and burnishing action, the teeth of the work gear are uniformly compacted and smoothed from end to end of the gear with less pressure than is required where a burnishing action only takes place.

The simultaneous shaving and burnishing of the working face surfaces of theteeth of the work gear to the desired high degree of accuracy and smoothness and compactness is, due to the multiplicity of cutting edges H and I2 and the high speeds of rotation of the cutters and work gears, accomplished in avery short time.

Assuming that the three helical cutters l, 8 and 9 eachhasthirty-one teeth, and, as illustrated, are provided with four spaced circumferential circular grooves II], it will be seen that each tooth of each cutter is divided by the four grooves into no less than five small shaving and burnishing teeth, each of which has four cutting or shaving edges; Therefore, since each tooth of each cutter is divided into'five small shaving or burnishing teeth having four cutting edges each, each tooth of each cutter will have twenty cutting edges, and since each cutter has thirtyone teeth it will have'a total of 620 shaving or cutting edges, 310 being the edges H and 310 being the edges I2. The three cutters L8 and '9 combined will,- of course, have in the aggregate 1860 shaving or cutting edges to act upon the working face surfaces .of the teeth ofthe work gear. I

On the basis of the shaving and burnishing operation consuming twelve seconds, and assuming that the cutters are rotated at a speed or 400 R. P. M. it will be obvious that the cutters will, during the twelve seconds required for the shaving and burnishing operation, each make eighty complete revolutions inmesh with the work gear, or a total combined number @1240 revolutions in mesh with the work gear.

In view of the multiplicity of cutting or shaving edges on each cutter and the aggregate large number of the cutting orshaving edges on the three cutters, it will readily be seen that the working face surfaces of the teeth'of the work gear are subjected to a great multiplicity of cut ting or shaving bites when the work gear isQrun .1

in mesh with the cutters and under pressure during the shavingor-burnishing'operation. T

Referring to the fragmentary developed view areaoae of the working face surface of one side of one of the teeth of the helical work gear 6, as illustrated in Fig. 4, the heavy lines a represent the cuts taken by the cutting edges formed in one of the cutters by the. grooves in, while the cuts taken by the cutting edges formed in the other cutters by the grooves m are represented by the lines l1 and 0, respectively. It will be understood thatthe distances between the lines a, b and c are exaggerated in the showing of Fig. 4, and actuallythe cuts represented by said lines would lie very closely'adjacent each other so that a slight axial movement of the cutters would cause the cuts in practice to overlap. The action of the cutting edges H and E2 of the cutters upon the working face surfaces of the teeth of the work gear is similar to the action of the cutting edges of the cutters upon the teeth of the work gear, as shown and described in my above mentioned copending application, Serial No. 9,824, and it is believed need not be explained in great detail herein. The cutting action of the cutting edges of the teeth ofthe cutter can be compared to the cutting action which would take place when a knife edge is brought into contact with a surface under pressure and successively moved \m'th small increments of advance across the surface, with the engagement between the knife edge and the surface likened to a series of shearing chops. Since each cutter is provided with a multiplicity of cutting edges spaced axially of the cutter, and since the cutting edges in each cutter of the plurality of cutters are staggered with respect to the cutting edges of each of the other cutters, a great number of cuts or shearing chops will be taken in the working face surface of the gear, and these cuts or chops will be so closely juxtaposed as to substantially overlap. However, since the cutters are arranged to have axial play or can be given a slight axial movement, the cuts or chops taken by the cut ting edges of the cutters in the working face surfaces of the teeth of the gear will overlap and extend from end to end of the teeth of the gear.

It will be seen that in the practice of the present invention gears can be finished in a minimum of time, since they are simultaneously shaved and burnished in a single operation.

Inasmuch as it is only necessary to give rotational movement to the intermeshed work gear and cutters, in addition to aradial pressure feed movement therebetween, while preferably allowing a slight axial play or imparting a slight axial relative movement to the cutters and gear, to simultaneously shave and burnish the work gear, theinvention maybe readily practiced and employed to simultaneously shave and burnish a wide varietyof gears, such as external and internal spur and helical gears, spline shaft gears, herringbone gears, and various other types of gears.

In Fig. of the drawing the cutters l3, I4 and i5 differ from the cutters I, 8 and 9 shown in Figs. 1 to 3 inclusive, in that they are in the form of spur gears, while the circular grooves spur cutters of-forming more acute cutting edges ll-"on the teeth of the 'cuttersthan would grooves "arranged at right angles to the axes of the. cutters. It will be understood that the cutters l3,"

l4 and i5 operate upon spur work gears in a manner similar to the operation of the cutters 1, 8 and 9 upon helical working gears, and that the grooves H in the various spur cutters are staggered or offset, and extend from the outside 5 diameters of the cutters to the roots of the teeth thereof. The expression cutters of gear form corresponding to the work gear as used in the description and claims hereof means that the cutters and the work gear are all of spur, helical or other gear form as distinguished for example from the cutters being of helical form and the work gear of spur form.

Although two' embodiments of the invention have been illustrated and described herein, it 15 should be understood that the invention is susceptible of various modifications and adaptations within the scope of the appended claims.

Having thus described my invention I claim: 1. The method of simultaneously shaving and 20 burnishing gears which comprises positioning a work gear in intermeshing relation with a plurality of cutters of gear form and each having a multiplicity of circumferential circular grooves extending throughthe teeth thereof and 25 forming a multiplicity of cutting edges and burnishing surfaces, the axes of the gear and cutters being arranged in parallel relationship, and then' rapidly rotating said intermeshed gear and cutters while applying radial pressure therebetween to simultaneously shave and burnish the working face surfaces of the teeth of the gear.

2. The method of simultaneously shaving and burnishing helical gears which comprises positioning a helical work gear in intermeshing rela- 35 tion with a plurality of helical cutters having a multiplicity of circumferential circular grooves extending through the teeth thereof and forming a multiplicity of cutting edges and burnishing surfaces, the axes of the cutters and gear being arranged inparallel relation and then rapidly rotatingsaid intermeshed gear and cutters while applying pressure radially therebetween to simultaneously shave and burnish the working face surfaces of the teeth of the gear.

3. The method of simultaneously shaving and burnishing gears which comprises positioning a work gear in intermeshing relation with a plurality of cutters of gear form and each having a multiplicity of circumferential circular grooves extending through the teeth thereof and forming a multiplicity of cutting edges and burnishing surfaces with the grooves of each cutter staggered or offsetwith respect to the grooves of the other cutters, the axes of the gear and cutters being arranged'in parallel relationship, and then rapidly rotating said intermeshed gear and cutters while applying radial pressure therebetween to simultaneously shave and burnish the working face surfaces of the teeth of the gear.

4. The method of simultaneously shaving and burnishing helical gears which comprises positioning a helical work gear in intermeshing relation with aplurality of helical cutters each having a multiplicity of circumferential circular grooves extending through the teeth thereof and forming a multiplicity of cutting edges and burnishing surfaces with the grooves of each cutter offset or staggered with respect to the grooves of the other cutters the axes of the cutters and gear being arranged in parallel relationship, and then rapidly rotating said intermeshed gear and cutters while applying pressure radially therebetween to simultaneously shave and burnish the working face surfaces of the teeth ofthe gear.

OLIVER G. SIMMONS. 

